 ; Helper constants.
 (defmacro EMPTY-STRING []     "")
 (defmacro SPACE        []    " ")
+(defmacro COMMA        []    ",")
+(defmacro POINT        []    ".")
 (defmacro NEW-LINE     []   "\n")
 (defmacro DBG-PREF     [] "==> ")
 (defmacro SPACE-       []  #"\ ")

        (when (seq words)
            (let [word     (first words)]
            (let [word-len (count word )]
            (let [word-pos (if (< (- pos 1) word-len) (subs word pos)
                                                      (EMPTY-STRING))]

            (println (str (DBG-PREF) word))

            (if (= word (last words)) (throw (Exception.  (str text- word)))
                                      (recur (rest words) (str text- (cond
                (< (- pos 1) word-len)
                    (let [word- (str (subs word 0 (- pos 1)) subst
                                     (subs word      pos  ))]

                    (println (str (DBG-PREF) word-))

                    word-)
                :else (do
                    (println (str (DBG-PREF) word ))

                    word))
                (SPACE))))

"evaluates to 'true'."
                     (EMPTY-STRING))]

    (let [pos   3] ; <== Can be set to either from 1 to infinity.
;   (let [subst "callable entity"]
;   (let [subst "AAA"]
;   (let [subst "+-="]
